1. Field of the Invention
The present invention relates to a method for manufacturing a nitride-based semiconductor device, and more particularly, to a method for manufacturing a nitride-based semiconductor device capable of increasing a breakdown voltage.
2. Description of the Related Art
The present invention is directed to a nitride-based semiconductor device and a method for manufacturing the same, and more particularly, to a structure of increasing a breakdown voltage and decreasing a leakage current in a GaN-based semiconductor device and a method for manufacturing the same.
Recently, gallium nitride (GaN), silicon carbide (SiC), and the like, which are wide band-gap materials, are being spotlighted in a field of power electric systems. Particularly, GaN has superior material properties to the other semiconductor materials, such as high critical electric field, high electron mobility, high electron saturation velocity, and the like, and thus it has been widely used for high-frequency, high-power, and high-temperature semiconductor devices.
Meanwhile, an AlGaN/GaN hetero-structure has a discontinuous conduction band between AlGaN and GaN and a high Two-Dimensional Electron Gas (2DEG) concentration due to a piezoelectric effect.
Accordingly, a High-Electron-Mobility Transistor (HEMT) and a lateral Schottky barrier diode manufactured on the AlGaN/GaN hetero-structure have a high 2DEG concentration (1013 cm−2) and a high critical electric field, and thus have been widely studied in fields of high-voltage switches and high-frequency amplifiers.
However, the conventional AlGaN/GaN HEMT has drawbacks in that the breakdown voltage and critical electric field are relatively low and thus the leakage current is relatively large. Moreover, the conventional AlGaN/GaN HEMT has drawbacks in that the normally-off state is difficult to maintain.
For these reasons, a Metal-Oxide-Semiconductor (MOS) structure was appointed as an appropriate structure for the high-voltage AlGaN/GaN HEMT, and thus studies on a gate insulating layer have been actively conducted. For example, SiO2, Si3N4 and the like were used for the gate insulating layer in the previous studies, but they are problematic since they need to be formed in a thin film type to achieve a low dielectric constant (k). However, the thin film type of gate insulating layer may cause hot carriers, resulting in a gate leakage current. Thus, the introduction of gate insulating layers capable of increasing the breakdown voltage and having a high on/off current ratio is required.
Meanwhile, the conventional nitride-based semiconductor adopted Ni for contacts. However, the nitride-based semiconductor including Ni contacts has a drawback of strong internal stress. Additionally, since Ni is easily oxidized, an additional component such as an Au layer needs to be laminated on Ni. Moreover, the inter-fusion between AlGaN/GaN and a metal material causes deterioration in electron characteristics during a high-temperature treatment procedure.
Moreover, the conventional semiconductor device has an internal resistance due to the distance between a source electrode and a gate electrode. For this reason, as the distance between the source electrode and the gate electrode increases, the internal resistance becomes greater, which may cause deterioration in on-resistance.
Accordingly, the development of semiconductor devices capable of decreasing an internal resistance due to the distance between the source electrode and the gate electrode is required.